U0121 = Data bus, anti-lock brake system (ABS) control module - no communicationSet Condition: The DTC will set if a valid CAN ID was not received in the from the ABS moduleor The ECM/PCM doesn't receive a Bus Message from the Anti-lock Brake Module.

U0415 = Invalid data received - anti-lock brake system (ABS) control moduleORU0415-Implausible data received from ABSSet Condition: When the TCM detects an incorrect CAN ID from the ABS control module.

U0402 = Invalid data received - transmission control module (TCM)Set Condition: An error message has been received over the bus from the Transmission Control Module (TCM). ORU0402–IMPLAUSIBLE DATA RECEIVED FROM TCM (FDCM)Set Condition: The Final Drive Control Module is receiving implausible data for gear or PRNDL position from the TCM------------------What happened right before you got the codes? Battery go dead? Jump start?Any recent Mods or changes you made?

Most of the above could be due to a chafed, loose, or burnt wire. If they are intermittent.If they are continuous, then most likely your ABS module or PCM is shot, or there are other modules which are not correctly programmed. (VIN Missing/Mismatch, TIPM, battery or ignition related)

Make sure you have + and - to the ABS module.Check fuses J6 and J7 are good and are seated correctly.The Black 47 way ABS module connector is inboard of the TIPM.Check the following Pins.Pin 1 (TN/RD wire) B+, Pin 13 (BK) -,Pin 25 (DG/RD wire) B+, Pin 38 (BK wire) -. Other then that you are looking at a dealer visit...

U0121 = Data bus, anti-lock brake system (ABS) control module - no communicationSet Condition: The DTC will set if a valid CAN ID was not received in the from the ABS moduleor The ECM/PCM doesn't receive a Bus Message from the Anti-lock Brake Module.

U0415 = Invalid data received - anti-lock brake system (ABS) control moduleORU0415-Implausible data received from ABSSet Condition: When the TCM detects an incorrect CAN ID from the ABS control module.

U0402 = Invalid data received - transmission control module (TCM)Set Condition: An error message has been received over the bus from the Transmission Control Module (TCM). ORU0402–IMPLAUSIBLE DATA RECEIVED FROM TCM (FDCM)Set Condition: The Final Drive Control Module is receiving implausible data for gear or PRNDL position from the TCM------------------What happened right before you got the codes? Battery go dead? Jump start?Any recent Mods or changes you made?

Most of the above could be due to a chafed, loose, or burnt wire. If they are intermittent.If they are continuous, then most likely your ABS module or PCM is shot, or there are other modules which are not correctly programmed. (VIN Missing/Mismatch, TIPM, battery or ignition related)

Make sure you have + and - to the ABS module.Check fuses J6 and J7 are good and are seated correctly.Black 47 way connector on the left inboard of the TIPM.Check the following Pins.Pin 1 (TN/RD wire) B+, Pin 13 (BK) -,Pin 25 (DG/RD wire) B+, Pin 38 (BK wire) -. Other then that you are looking at a dealer visit...

Thank you i will go down that list tomorrow

First time it happened i only had the code u0121 when i was driving and then nothing for a long time maybe a few months. Then the second time i got the u0121 on a morning going to start the car. 3rd the same but today the 4th time it came up with all 3 while i was driving but also lost the speedo as well after say 10 meters the speedo came back and only the abs and engine light were on the dash. after clearing codes each time nothing shows up.

Other stuff that maybe related .Radio randomly resets time after a few days .Last week the power seats forward would not work until i pressed the memory button (This also caused the radio to reset) and after worked fine. I keep testing the seat and it works perfect only that one time it did not work and reset the radio.

The problem with CAN (computer communication) errors is that you need special tools to check them. Intermittent errors are the hardest to track down. Clock time is not controlled by the radio believe it or not. Time is actually integrated in to the WCM (wireless control module). How do I know this? Well my rig looses about 5 minutes each month. Dealer has a TSB to fix the time loss. But to fix it they need to replace the WCM and program the new one.Clock time is displayed on the radio VIA the CAN from the WCM.

With all the (intermittent) communication errors, I am leaning more and more toward a loose, chafed, or corroded wire on the CAN "C" network as the problem.

The hard part is tracking down the guilty wire.

Since we are aware of 1 instance where one action caused another reaction, lets start there.Disconnect the Neg (-) battery cable. Wait 10 minutes. (VERY IMPORTANT! The wires under the front seats are integrated with the airbag system.)Then check under the front seat for a pinched/cut wire.

I think you are right with it beeing a wire at fault because it happens totally random

Today.Time reset again this morning after putting it right last night normally takes longer for it to reset.Removed driver seat and checked all wires and connections .Removed center console and found someone had been using one of the mounts for the (56029433ab) module for ABS as a ground for a rear 12v supply so removed that.

Bummer!The TIPM is the main junction point of the CAN "C" BUS.So here is something you can try.Disconnect the Neg(-) battery cable.Disconnect the Pos (+) battery cable.Disconnect the Pos (+) battery cable at the TIPM.

Release the TIPM retaining clips and roll the TIPM over.Look for the "C1" connector. It is black 50 way. This is the one that has the CAN C bus connections on it. Release the locking arm carefully! It is not strong, and may break. You may have to wiggle the connector and pull on it while releasing the arm.

Look at Pins 15 and 16, 15 is WT/LB wire CAN -, 16 is WT/BK wire CAN +. Check for corrosion in the plug and on the TIPM Pins. DO NOT insert anything into the plug wire holes! This will make them to big to make a good connection.

While looking at the TIPM, check the wires under there for chafing.When I did my lift, I found a wire that was rubbing on my TIPM bracket. Luckily it was before it went all the way thru the insulation. In my case the wire was rubbing on the rear inboard side of the bracket... Anyway, check them out.If it all looks good, put everything back in reverse order from above.Good luck. I hope it is a simple chafed wire under there...

Bummer!The TIPM is the main junction point of the CAN "C" BUS.So here is something you can try.Disconnect the Neg(-) battery cable.Disconnect the Pos (+) battery cable.Disconnect the Pos (+) battery cable at the TIPM.

Release the TIPM retaining clips and roll the TIPM over.Look for the "C1" connector. It is black 50 way. This is the one that has the CAN C bus connections on it. Release the locking arm carefully! It is not strong, and may break. You may have to wiggle the connector and pull on it while releasing the arm.

Look at Pins 15 and 16, 15 is WT/LB wire CAN -, 16 is WT/BK wire CAN +. Check for corrosion in the plug and on the TIPM Pins. DO NOT insert anything into the plug wire holes! This will make them to big to make a good connection.

While looking at the TIPM, check the wires under there for chafing.When I did my lift, I found a wire that was rubbing on my TIPM bracket. Luckily it was before it went all the way thru the insulation. In my case the wire was rubbing on the rear inboard side of the bracket... Anyway, check them out.If it all looks good, put everything back in reverse order from above.Good luck. I hope it is a simple chafed wire under there...

Its run perfect for a week since beeing at garage now its back worse then ever i tried c1 connector but seems to be ok.The ground behind the left headlight was heavily corroded so i also cleaned that up but made no difference.

I'm out of ideas short of chasing wires or replacing modules one by one at this point.There are tests that a dealer can run with their scanner. But the fault has to happen during the tests. If the tests turn out inconclusive, the manual has them run continuity tests from plug to plug on each module reporting the lost communication.As you can imagine the costs of having them do this adds up real quickly.

I'm out of ideas short of chasing wires or replacing modules one by one at this point.There are tests that a dealer can run with their scanner. But the fault has to happen during the tests. If the tests turn out inconclusive, the manual has them run continuity tests from plug to plug on each module reporting the lost communication.As you can imagine the costs of having them do this adds up real quickly.

I really appreciate the help and ideas you have given me thank you.

I went again today to get it wiped then i drove around for 180klm and it went on and off twice only once into limp mode.It was scanned again and there was around 8 faults relating to lost communication with abs module(wix scanner)

They said to replace the abs module but could not guarantee that would fix it. Found a few places that can repair them or even if i open it up and re solder it myself. or get a second hand one just worried i have to take it to the dealer to get the vin paired if i get a used one.

I got a replacement off ebay and went to get it programmed but its come back as faulty showing a code for brake pressure switch as well as vin mismatch. So looks like sending it back and getting another one.

I got a replacement off ebay and went to get it programmed but its come back as faulty showing a code for brake pressure switch as well as vin mismatch. So looks like sending it back and getting another one.

It will have a VIN missmatch until it is initialized. Not sure if the pressure switch error will correct once the ABS has the correct VIN.

I got a replacement off ebay and went to get it programmed but its come back as faulty showing a code for brake pressure switch as well as vin mismatch. So looks like sending it back and getting another one.

It will have a VIN missmatch until it is initialized. Not sure if the pressure switch error will correct once the ABS has the correct VIN.

I went to him to get the module initialized but then when i got there he said because it shows the pressure switch code he will not be able to set it up. No idea if that is true or not but i did see the codes come up on the scanner for pressure switch. I was thinking it would go away after but my only alternative is to take it to a jeep dealer now as nobody else has the scanner.

I think i maybe found the problem when the guy scanned the abs and found the pressure sensor code. I completely forgot that the other garage never scanned the abs they only scanned the car. So i swapped over the pump that came with the replacement module and see if i get the code again.

I believe what was happening was the pressure sensor in the abs pump was intermittently failing and causing the abs module to shut down thats why i was getting u0121 lost communication.